Endless conveyor belts, particularly those involved in removing particulate material such as grain, dirt, etc., utilize single or multiple belt scrapers, normally positioned so that the longitudinal axis of the scraper extends generally transversely across the bottom surface of the endless conveyor belt bottom run. The scraper, in contacting material clinging to that bottom surface, releases the material from the belt surface which falls by gravity into a collecting area beneath the belt at the location of the scraper.
Many belt scrapers consist of one or several scraper blades supported by an apparatus which includes some type of biasing means for pressing the edge of the scraper blade into contact with the surface of the belt to be scraped. Such apparatus may be of the weight applying counter-balance type, rotating spring type or linear biasing type. The various types have certain advantages, but some disadvantages, depending on the environment of use, material to be scraped, type of blade, width of belts, etc. Many of these belt scrapers are fairly complicated and relatively expensive. As may be appreciated, during use, in spite of the bias employed to maintain the edge of the scraper blade in contact with the surface of the belt, the scraper blade may be worn unevenly, and it is difficult to maintain the scraper blade (or multiple scraper blades of sectional form) in edge contact with the belt sufficient to ensure a nearly 100% removal of the clinging material during belt movement across the edge of the blade or blades.
U.S. Pat. No. 4,987,993, issued Jan. 29, 1991, is representative of the state of the art and utilizes a leaf spring as a biasing means for biasing a separate scraper blade member towards and away from the belt to be cleaned. The belt scraper of that patent utilizes an elongate frame defining an elongate aperture, with the blade member guided for movement within and transversely of the aperture so as to move towards and away from the belt to be cleaned. Mounting means are provided in the vicinity of the ends of the frame for mounting the frame relative to the belt. A spring support pivotally connected to the frame bears a spring which engages the scraper blade member and in turn presses it outwardly of the aperture towards the belt being cleaned.
While such arrangement is fairly simple, the blade is, at most, contacted at two positions over the length of the blade by the leaf spring and there is no assurance that the blade edge opposite to that being contacted by the spring will engage the belt over the full length of the blade. Further, since the scraper blade is physically separate from the biasing spring, dirt and/or water entering the area interferes with the free movement of the blade relative to its support, and indeed the blade relative to the spring, increasing the likelihood of uneven spring biasing force application to the movable blade and tilting of the blade relative to the surface of the moving belt, with attendant jamming.